The present invention relates to a method and system for detecting faults in a brushless exciter and, particularly, relates to a wireless temperature sensing diode fault detector for a brushless exciter.
A brushless excitation system (or more simply a “brushless exciter”) applies a direct current (DC) to the field coils of a rotor in an electrical machine. The current in the generator rotor field coils generates an electromagnetic field that induces current in, for example, the coils of a stator surrounding the generator rotor and in a generator producing AC current. Alternatively, the electromagnetic field from the rotor field coils may be used to turn the rotor of a motor.
Typically, a brushless excitation system is mounted on and rotates with the rotor of the electrical machine. The brushless excitation system includes a rotating armature and a diode rectifier, which may be configured as a diode wheel. Alternating current (AC) generated within the brushless exciter rotating armature is converted by the rotating diode rectifier to direct current, which is applied to the field windings of the generator rotor.
A fault in a diode of the rectifier can impair the conversion of AC to DC by the rectifier. A diode rectifier typically has two or more redundant diodes connected in series for each phase of the AC power applied to the input to the rectifier. It is generally difficult to reliably detect a fault in one diode, due to the presence of redundant diodes. The failure of a single diode may not substantially reduce the ability of the rectifier to convert AC to DC power. The failure of two or more diodes in series can impair the conversion of AC to DC, lead to a failure of the rectifier and result in an unscheduled shutdown of the electrical machine.